Re: [DISCUSS] Should RFCs for new functions include a userland polyfill/reference implementation?

On Tue, Aug 25, 2026, at 6:18 AM, سپهر محمودی wrote: > Hi internals, > > While reviewing various RFCs that introduce new functions, I noticed an > inconsistency: some authors include a userland polyfill (reference > implementation) in their RFCs, while others do not. > > I wanted to open a discussion on whether we should strongly encourage > RFC authors to provide a PHP userland implementation when proposing new > standard library functions, **where technically feasible**. > > Of course, I understand that this isn't possible for every new > function—especially those that interact with low-level OS APIs, memory > management, or internal engine features. However, for functions dealing > with arrays, strings, math, or general logic, I believe this has a > couple of major benefits: > > 1. It clarifies the exact intended behavior, including edge cases and > type coercions, making the proposal easier to understand without diving > into the C implementation. > 2. It immensely helps the community (e.g., the Symfony polyfill team) > to quickly and accurately port the function to older PHP versions once > the RFC is accepted. > > Should we consider adding this as a standard recommendation (e.g., > "Reference Implementation") in the official RFC template for applicable > functions? > > I would love to hear your thoughts on this. > > Best regards, > Sepehr Interesting idea. I think "recommended where relevant, but not required" is a reasonable policy to have. As noted, many RFCs don't have polyfillable features. For those where it is feasible, I think the "make it clear what the logic is" angle is the most compelling. (I often do that in the non-polyfill RFCs to help clarify the behavior.) And it would also give us a target to benchmark against to see if putting it in C really has a performance benefit. --Larry Garfield